Comprehensive multigene phylogenies of excavate protists reveal the evolutionary positions of "primitive" eukaryotes

被引:130
作者
Simpson, AGB [1 ]
Inagaki, Y
Roger, AJ
机构
[1] Dalhousie Univ, Canadian Inst Adv Res, Program Evolutionary Biol, Halifax, NS B3H 1R2, Canada
[2] Dalhousie Univ, Dept Biol, Halifax, NS, Canada
[3] Univ Tsukuba, Ctr Computat Sci, Tsukuba, Ibaraki 305, Japan
[4] Univ Tsukuba, Inst Biol Sci, Tsukuba, Ibaraki 305, Japan
[5] Dalhousie Univ, Dept Biochem & Mol Biol, Halifax, NS, Canada
关键词
eukaryote evolution; Giardia; mitochondria; Protozoa; tubulin;
D O I
10.1093/molbev/msj068
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Many of the protists thought to represent the deepest branches on the eukaryotic tree are assigned to a loose assemblage called the "excavates." This includes the mitochondrion-lacking diplomonads and parabasalids (e.g., Giardia and Trichomonas) and the jakobids (e.g., Reclinomonas). We report the first multigene phylogenetic analyses to include a comprehensive sampling of excavate groups (six nuclear-encoded protein-coding genes, nine of the 10 recognized excavate groups). Excavates coalesce into three clades with relatively strong maximum likelihood bootstrap Support. Only the phylogenetic position of Malawimonas is uncertain. Diplomonads, parabasalids, and the free-living amitochondriate protist Carpediemonas are closely related to each other. Two other amilochondriate excavates, oxymonads and Trimastix, form the second monophyletic group. The third group is comprised of Euglenozoa (e.g., trypanosomes), Heterolobosea, and jakobids. Unexpectedly, jakobids appear to be specifically related to Heterolobosea. This tree topology calls into question the concept of Discicristata as a supergroup of eukaryotes United by discoidal mitochondrial cristae and makes it implausible that jakobids represent an independent early-diverging eukaryotic lineage. The close jakobids-Heterolobosea-Euglenozoa connection demands complex evolutionary scenarios to explain the transition between the presumed ancestral bacterial-type mitochondrial RNA polymerase found in jakobids and the phage-type protein in other eukaryotic lineages, including Euglenozoa and Heterolobosea.
引用
收藏
页码:615 / 625
页数:11
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